The invention relates to a method for controlling a pressure control device of a pressure-medium-type brake system of a vehicle.
A method of said type or a pressure control device of said type is known from German patent document no. DE 10 2010 010 606 A1. The known pressure control device is constructed such that, proceeding from a brake slip regulation (ABS) arrangement as a basis, said pressure control device can be easily enhanced in terms of its regulation functions merely through the addition of individual components, for example for enhancement to include drive slip regulation (ASR), driving dynamics regulation (ESP) or an electronic brake system (EBS).
The known pressure control device comprises a single relay valve, having a reservoir port which is supplied from a reservoir pressure, having a deaeration port which is connected to a pressure sink, having a control port, and having at least two working ports, wherein one working port is assigned to at least one brake cylinder of a wheel of one vehicle side of the axle, and the other working port of the single relay valve is assigned to at least one brake cylinder of a wheel of the other vehicle side of the axle. Each working port of the relay valve is connected to a 2/2 directional valve which is controlled directly or indirectly by a control unit and which is assigned to in each case one vehicle side and which, in a manner dependent on the actuation by the control unit, either produces a connection between the respective working port of the relay valve and the associated brake cylinder or shuts off said connection, and wherein the control port of the relay valve is, by way of a valve device which is formed by a 3/2 directional solenoid valve or by two 2/2 directional solenoid valves and which is controlled by way of the control unit, connectable either to a brake control pressure formed dependently on a driver braking demand, or to a pressure sink.
Thus, the known pressure control device comprises just four basic elements: the single relay valve, the valve device, which comprises only one 3/2 directional solenoid valve or two 2/2 directional solenoid valves, and the two 2/2 directional valves. By means of these valves, which are relatively easy and inexpensive to produce, it is already possible to realize wheel-specific brake slip regulation to a certain extent, that is to say for example a pressure build-up or pressure dissipation at a wheel brake cylinder of one vehicle side with simultaneous holding of a pressure in a wheel brake cylinder of the other vehicle side. An opposite pressure profile (pressure dissipation, pressure build-up) at wheels on different vehicle sides is however not possible.
In particular, only a single relay valve is used in order to realize wheel-specific control of large pressure medium cross sections in the brake cylinders inter alia by way of a central, relatively small control pressure flow. In this way, the pressure control device is, altogether, very inexpensive to produce.
In the control of the known pressure control device, however, the problem arises that, owing to the relatively inert reaction of the relay valve to pneumatic pressure control signals introduced through its control port, a situation may for example arise in which compressed air continues to flow into a brake cylinder despite the fact that a pressure dissipation is already sought there in a manner commanded, for example, by a wheel-specific brake slip regulation (ABS) arrangement. This is disadvantageous in particular with regard to a demanded fast pressure adaptation of the brake pressures in the brake cylinders in the context of a brake slip regulation (ABS) arrangement, a drive slip regulation (ASR) arrangement or a driving dynamics regulation (ESP) arrangement.
The invention is accordingly based on the object of further developing a method for the control of a pressure control device mentioned in the introduction such that said method permits faster adaptation of the brake cylinder pressures.